body,
div,
dl,
dt,
dd,
ul,
ol,
h1,
h2,
h3,
h4,
h5,
h6,
pre,
form,
fieldset,
legend,
input,
textarea,
button,
p,
blockquote,
th,
td {
  margin: 0;
  padding: 0;
}

body {
  text-align: center;
}

li {
  list-style-type: none;
}

a {
  text-decoration: none;
  color: #333;
}

img,
input,
button {
  border: none;
  vertical-align: middle;
}

/* s使用伪元素清除浮动 */
.clear::after {
  content: "";
  display: block;
  clear: both;
}